WO2000048244A1 - Device and method for heat-treating wafer - Google Patents

Abstract

Issues: A device and method for heat-treating a wafer which can restrain a stress to be caused by the self-weight of a wafer when the wafer is increased in diameter and in treating temperature, which can be less susceptible to a thermal stress effect, and which can prevent slippage at contact portions between the wafer and a wafer boat when heat-treated in a vertical diffusion furnace and a vertical vapor growth furnace to eliminate effects on device characteristics by the slippage and significantly enhance a yield of the device. Solutions: A wafer boat (3) for a vertical furnace which disposes a plurality of vertical columns (4), and which places wafers (2) respectively on generally planar column supports (41) provided at preset intervals at these columns (4), wherein columns (4b, 4c) in the front-most row in a wafer receiving direction have a bow shape or partially bow shape at the cross-sections of column bodies (40b, 40c), and the column supports (41b, 41c) are provided at the front ends of the column bodies (40b, 40c) in the wafer receiving direction.

Description

 Specification

 Wafer heat treatment apparatus and heat treatment method

Technical field

 The present invention relates to a heat treatment apparatus and a heat treatment method having a wafer boat, and more particularly to a vertical diffusion furnace and a vertical vapor deposition furnace having a vertical wafer boat and a heat treatment method therefor. Background art

 The present invention relates to a heat treatment apparatus and a heat treatment method having a wafer boat, and more particularly to a vertical diffusion furnace and a vertical vapor deposition furnace having a vertical wafer boat and a heat treatment method therefor.

 In the process of oxidizing and diffusing semiconductor wafers, a large number of semiconductor wafers are loaded on a wafer boat, and the wafer boat is directly loaded into a diffusion furnace, where a predetermined heat treatment is performed. Depending on the type of diffusion furnace, vertical wafer boats or horizontal wafer boats are used.

The conventional vertical wafer boat has a problem that, at a support portion in contact with the wafer, thermal distortion is applied to the wafer due to a difference in heat conduction between the wafer and the support portion of the wafer boat, thereby causing a crystal defect. . In order to solve this problem, the wafer boat has a structure that supports wafers at three or four points. A wafer boat force ^{s is} used to make contact between the boat support and the support portion (see Japanese Patent Application Laid-Open No. S61-191015). Further, a groove slightly thicker than the thickness of the wafer is formed in the boat support, and a peripheral edge of the wafer and a periphery of the rear face of the wafer are supported in surface contact with the groove.

On the other hand, as the diameter of wafers has increased, especially 30 cm (12 inches) or more In such a case, there is a problem that the wafer warps due to its own weight, and eventually crystal defects such as slip occur. To solve this problem, the position was used © Ehabo one crossing ^s adapted to support a wafer at closer to the center from the periphery of the wafer (JP-A-6 1 6 9 0 1 0 JP, Japanese Patent Application Laid-Open No. Hei 91-139352).

When heat-treating a wafer, heat transfer from the furnace also occurs at the point of contact with the force-supporting member by radiation or heat transfer, causing unevenness in the temperature distribution of the wafer. The non-uniform temperature distribution of the wafer generates thermal stress on the wafer, causing crystal defects, and also adversely affects the heat treatment, such as making the film thickness non-uniform. The occurrence of such a defective portion near the center of the wafer is greater than that at the outer peripheral portion in terms of product yield and countermeasure cost by ⁵ '. However, when the above-described conventional technique in which the wafer is supported at a position closer to the center from the periphery of the wafer is used, there is a problem that the possibility that a defective portion is generated near the center increases. In addition, providing a deep slit or support bar on the column to support the inside of the cylinder has a problem that the processing is troublesome and the cost is increased. Therefore, it is necessary to support the vicinity of the wafer as much as possible and suppress the occurrence of crystal defects such as slips.

 In addition, in order to insert a wafer into a wafer boat, at least one space between adjacent columns must secure an interval to receive the wafer, which restricts the supporting position of the wafer. For this reason, it was not possible to support the optimal support position, and as a result, there was a problem that high stress was generated. Disclosure of the invention

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems, and to suppress the generation of stress due to the weight of the wafer when the diameter of the wafer is increased and the processing temperature is increased, so that the wafer is less affected by thermal stress. And a vertical diffusion furnace and a vertical vapor phase growth furnace Heat treatment apparatus and heat treatment that can prevent the occurrence of slip at the contact portion between the wafer and the wafer boat during heat treatment in the above, eliminate the effect of the slip on device characteristics, and bring about a remarkable effect on the improvement of device yield Is to provide a way.

 The present invention comprises a plurality of pillars arranged in a longitudinal direction, and a wafer boat for loading a wafer on each of substantially column-shaped pillar support portions provided at predetermined intervals on the pillars. In a heat treatment apparatus for performing a predetermined heat treatment on the wafer in a state where the wafer is supported by the wafer boat, the column in the front row of the wafer boat in the wafer receiving direction has a cross section of the column main body having a substantially bow shape or a substantially partial bow shape. This is a heat treatment device.

 Further, the present invention includes a wafer boat in which a plurality of columns are arranged in a vertical direction, and wafers are respectively loaded on substantially flat column-shaped column supports provided at predetermined intervals on the columns. In a heat treatment apparatus for performing a predetermined heat treatment on a wafer while supporting a wafer by a wafer boat, the support in the front row of the wafer receiving direction of the wafer boat has a pillar supporting portion provided at a front end of the pillar body in the wafer receiving direction. It is a heat treatment apparatus.

 According to the present invention, ボ ー ト the total number of pillars of the boat is three, and 接触 the contact support position of the pillar support portion of the pillar in the front row in the wafer receiving direction, which is in contact with and supports the lower surface of the wafer, is When heat treatment is performed at a center angle between the contact support position of the column support at the backmost position in the direction and the contact support position near 950 ° C, 100 ° to 135 °, preferably 117 ° This is a heat treatment apparatus that is located at a position between 110 ° and 127 °, preferably 117 ° when the wafer is heat-treated at around 100 ° C.

 Further, the present invention is the heat treatment apparatus, wherein the column support portion has a support protrusion, and the support protrusion is supported in point contact with the wafer.

Further, the present invention is the heat treatment apparatus, wherein the support member is supported in line contact with the wafer. Further, the present invention is the heat treatment apparatus, wherein the column support section supports the wafer in surface contact.

 Further, the present invention provides a heat treatment method of performing a predetermined heat treatment on a wafer while supporting the wafer at three points, namely, two points in the front row of the wafer receiving direction and one point at the back of the wafer receiving direction. If the center position of the support position in the front row in the wafer receiving direction and the center position of the backmost support position in the wafer receiving direction is 950 and heat treatment is performed in the vicinity, 100 ° to 135 °, preferably 1 1 When the heat treatment is performed in the vicinity of 100 °, the heat treatment is performed at a position of 110 ° to 127 °, preferably 117 °. is there. BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is an explanatory view of the overall configuration of a vertical wafer boat according to a first embodiment.

FIG. 2 is an explanatory longitudinal sectional view of a vertical diffusion furnace (vapor phase growth furnace) using the vertical furnace wafer boat of Example 1.

FIG. 3 is an explanatory plan view showing a column of the vertical wafer boat of the first embodiment.

FIG. 4 is an explanatory diagram showing the relationship between the central angle of wafer support and the generated stress in Example 1. FIG. 5 is an explanatory plan view showing a vertical wafer boat according to a second embodiment.

FIG. 6 is an explanatory sectional view showing a vertical wafer boat according to a third embodiment.

FIG. 7 is an explanatory sectional view showing a vertical wafer boat according to a fourth embodiment.

FIG. 8 is an explanatory cross-sectional view showing a vertical boat of the fifth embodiment. BEST MODE FOR CARRYING OUT THE INVENTION

 An embodiment of the present invention will be described.

 A preferred embodiment of the heat treatment apparatus of the present invention will be described with reference to FIGS.

Example 1 will be described. As shown in FIG. 1, the vertical furnace wafer boat 3 of the present embodiment includes three support columns 4, a top plate 31, a bottom plate 32, a cap 33, and the like. Have. Fig. 2 shows a vertical sectional view of the vertical furnace in use. In FIG. 2, a reaction tube installed in a vertical resistance heating furnace 11 has a double structure composed of an outer tube 12 and an inner tube 13, and is held by a frame 14. . The reaction gas is supplied into the inner tube 13 and collected from the tube 12. The wafer boat 3 is installed in the inner tube 13, and is inserted and withdrawn from a circular hole 15 provided at the center of the gantry 14. The wafer 2 is held on the wafer boat 3 at an arbitrary interval above and below. The wafer 2 of the wafer boat 3 pulled out from the inner tube 13 is taken in and out by the transfer device.

The arrangement of the support 4, the support main body 40 and the support 41 in the wafer boat 3 of this embodiment will be described with reference to FIG. FIG. 3 is a cross-sectional view of the wafer boat 3, which is a cross-sectional view taken along line AA in FIG. The boat 3 supporting the wafer 2 has three columns 4 a, 4 b, and 4 c composed of a column body 40 and a column support 41. The columns 4a, 4b, and 4c are provided so as to stand substantially vertically around the periphery of the ヱ ヱ c2. The support 4a, which is farthest in the receiving direction of C, is provided so as to face the receiving direction of C, and the supports 4b, 4c in the front row in the wafer receiving direction are provided symmetrically with respect to the wafer receiving direction. ing. The column support portions 41b and 41c are provided at the front end in the receiving direction from the column body portions 40b and 40c, respectively, and extend laterally inward toward the wafer side. It is overhanging. The contact support position for supporting and supporting the lowermost column support portion 41a and the front row column support portion 41b, 41c in contact with the lower surface of the wafer 2 is as follows. , The central angle is 110. It is arranged to be ~ 127 °, and preferably to 117 °. Further, when the heat treatment temperature is around 950, it is preferable that the central angle is set to 100 ° to 135 °, and more preferably to 117 °. As a result, the decomposition shear stress generated in the wafer becomes less than the critical decomposition shear stress, and no slip occurs. Hereinafter, the contact support position of the column in the column support portion will be described. The silicon (S i) wafer slip is dominated by twelve slip systems with a slip plane of il 1 た め, since the silicon crystal is a single crystal with a face-centered cubic lattice. The shear stress in the slip direction is called the decomposition shear stress. The minimum decomposition shear stress at which slip occurs is called critical decomposition shear stress. In a 100 o ° c atmosphere, a 0.5 mm thick wafer of approximately 30 cm (12 inches) is supported at various center angles with a position 90% outside the radius from the center of the backside of the wafer at various center angles. Figure 4 shows the ratio of the shear stress of the sample to the critical shear stress at 1 000 ° C. Decomposed shear stress was obtained by calculation using the finite element method. As shown in Fig. 4, the ratio of the decomposed shear stress generated at c and the critical decomposed shear stress at 1000 ° C is minimized at 117 °. When the ratio of the decomposition shear stress to the critical decomposition shear stress at 1000 is less than 1.0, the decomposition shear stress falls below the critical decomposition shear stress. Therefore, between about 110 ° and 127 °, the decomposition shear stress due to its own weight can be lower than the critical decomposition shear stress. Similarly, when the heat treatment temperature is around 950 ° C, it is possible to reduce the decomposition shear stress due to its own weight below the critical decomposition shear stress between about 100 ° and 135 °, and the minimum is 1 1 7 °.

Next, the structure of the column in the boat according to the present embodiment will be described with reference to FIG. The columns 4a, 4b, and 4c bend toward the center of the wafer due to their own weight and the mass of the wafer. In particular, when quartz glass is used as a boat material, at a treatment temperature of 1000 or more, the quartz glass exhibits a viscoelastic behavior beyond the strain point. In such a state, the strain increases in proportion to the reciprocal of the viscosity, the stress and the holding time, so that it remains as a permanent deformation after unloading. The deformation due to the bending stress due to the radial deflection of the columns 4a, 4b, and 4c remains as the deflection of the columns 4a, 4b, and 4c, and is accumulated by repeated heat treatment, and finally holds the wafer 2. The deformation becomes impossible. To extend the life of the wafer port 3, increase the radial moment of inertia of the columns 4a, 4b, and 4c. However, the increase of the second moment of area causes the increase of the cross-sectional area. The support 4a at the innermost position in the receiving direction in the present embodiment has a substantially trapezoidal or substantially circular cross-sectional shape, and has a support portion 41a at the center of the support body 4'0a. In order to increase the second moment of area of the column 4a in the radial direction of the wafer, it is most effective to increase the width in the radial direction. However, to increase the width in the radial direction boat ^径Ka? Increases, also increases the size of the apparatus itself, causing a cost increase. Therefore, the length may be increased in the circumferential direction. The supporting columns 4b and 4c in the front row of the receiving direction have a substantially trapezoidal or substantially arc-shaped cross-sectional shape like the supporting column 4a at the back, and the supporting portions 41b and 41c are columns. If the length is increased in the circumferential direction to increase the second moment of cross section, there is a possibility that it will be an obstacle to wafer acceptance.ゥ ヱ If you do not hinder reception, you will not be able to support the optimal support position. As with the innermost support 4a, increasing the width in the radial direction increases the boat diameter and the size of the equipment itself, which increases costs. Therefore, the cross-sectional shapes of the columns 4b and 4c are set to be substantially arcuate or substantially partial arcuate. When the cross-sectional shape is substantially arcuate or partial arcuate, the outer peripheral side is a circular shape and the inner peripheral side is parallel to the receiving direction. Then, a column support is provided at the front end of the column main body in the wafer receiving direction. This makes it possible to support the wafer at the optimum support position without increasing the boat diameter and without obstructing wafer reception, and to provide a sufficient second moment of area.

Second Embodiment A wafer boat according to a second embodiment will be described with reference to FIG. In this embodiment, the shape of the pillar main bodies 50b and 50c of the pillars 5b and 5c is the same as that of the pillar main bodies 40b and 40c of the pillars 4b and 4c in the first embodiment. than even the force that is to increase the length to the wafer receiving incoming ^direction?, the cross-sectional shape is Ru substantially arcuate or substantially partially arcuate der. Thereby, the secondary moment of section can be further increased as compared with the columns 4b and 4c in the first embodiment.

Embodiment 3 will be described with reference to FIG. Fig. 6 shows a radial section of post 6 FIG. The support portion 61 of the column has a point-like projection 6 11. In order to reduce the slip occurrence caused by uneven due to thermal stress in the temperature distribution due to contact between the supporting portion 61 and the wafer 2, that force ⁵ 'desirable to reduce the contact area between the support and the Uweha a heat treatment process . Since the support portion 61 in the present embodiment has the point-like projections 6 1 1, the contact between the support portion 6 1 and the contact 2 becomes a point contact by the point-like protrusions 6 1 1, thereby reducing the contact area and reducing slippage. The effect of thermal stress can be reduced. The same applies to the column 6a in the receiving direction and the columns 6b and 6c in the front row.

 Example 4 will be described with reference to FIG. FIG. 7 is a radial cross-sectional view of the column 7. The support portion 71 of the column has a linear projection 71 1 having a ridge at a position where the distance from the center of the wafer is constant. Since the support portion 71 in the present embodiment has the line 4 dog protrusion 7 1 1, the contact between the support portion 7 1 and ゥ ヱ c 2 is line contact by the linear protrusion 7 1 1, as in the third embodiment. In addition, the contact area can be reduced, and the influence of thermal stress on the slip can be reduced. The same applies to the support 7 as the support 7a at the innermost position in the receiving direction and the supports 7b and 7c in the front row. Example 5 will be described with reference to FIG. FIG. 8 is a radial sectional view of the column 8. The support portion 81 of the column has a taper 811. In this embodiment, since the contact between the support portion 81 and the base 2 is a surface contact by the taper 811, the contact area is reduced as in the case of the third and fourth embodiments, and the thermal stress against the occurrence of slip is reduced. Can be reduced. The same applies to the support 8 as to the support 8a at the back of the receiving direction and the supports 8b and 8c in the front row.

 In the above embodiment, the support portion of the column in the vertical furnace wafer boat has been described as being integral with the column main body. However, it is possible to use a separate support member. Action and effect can be obtained. In addition, the total number of struts has been described as three, but other numbers may be used.

According to the present invention, the diameter of the wafer is increased and the wafer when the processing temperature is increased It suppresses the generation of stress due to its own weight and makes it less susceptible to the effects of thermal stress. Also, during heat treatment in vertical diffusion furnaces and vertical vapor phase growth furnaces, slip at the contact between wafer and wafer boat It is possible to obtain a heat treatment apparatus and a heat treatment method that can prevent the occurrence of the slip, remove the influence of the slip on the device characteristics, and significantly improve the yield of the device.

Claims

The scope of the claims 1. A plurality of columns are arranged in a vertical direction, and a wafer boat is mounted on each of the pillars, which is provided at a predetermined interval on each of the pillars. The wafer boat supports the wafers. In the heat treatment apparatus for performing a predetermined heat treatment on a wafer in a state where the support is provided, the support in the front row in the receiving direction of the support boat has a cross section of the support main body having a substantially bow shape or a substantially partial bow shape. apparatus.  2. A plurality of columns are arranged in a vertical direction, and a wafer boat for loading wafers on a substantially flat column-shaped column supporting portion provided at a predetermined interval on the columns is provided. In the heat treatment apparatus for performing a predetermined heat treatment on the wafer while supporting the wafer, the pillar in the frontmost row of the wafer boat in the receiving direction has a pillar supporting portion provided at a front end of the pillar body in the wafer receiving direction. A heat treatment apparatus characterized by the above-mentioned.  3. The heat treatment apparatus according to claim 1, wherein the total number of the pillars of the wafer boat is three, and the contact support for contacting and supporting the lower surface of the wafer in the pillar support portion of the pillar in the front row in the wafer receiving direction. When the wafer is heat-treated near the center angle of the contact support position of the column support portion of the column at the backmost position in the wafer receiving direction of 950 t: 100 ° to 135 °, desirably, 110 °, and 100 ° O: When heat treatment is performed in the vicinity, the position is set to 110 ° to 127 °, preferably, 117 °. Heat treatment equipment. 4. The heat treatment apparatus according to claim 1, wherein the column support portion has a support protrusion, and the support protrusion is supported in point contact with the wafer. 5. The heat treatment apparatus according to claim 1, wherein the support member is supported in line contact with the support. 6. The heat treatment apparatus according to claim 1, wherein the support column supports the wafer and the surface. A heat treatment apparatus characterized in that it is supported in contact. 7. In the heat treatment method of performing a predetermined heat treatment on the wafer while supporting the wafer at two points in the front row of the wafer receiving direction and one point at the back of the wafer receiving direction, When performing heat treatment near 950 ° C with a central angular force of ⁵ 'to the backmost support position in the front row, the support position in the front row should be 100 ° to 135 °, preferably 117 °, and 100 Ot: A heat treatment method characterized in that when performing a wafer heat treatment in the vicinity, the position is set at 110 ° to 127 °, preferably at 117 °.